It has been taught that presence in microchannel plate glass of "alkali elements with substantial radio isotope content (e.g., potassium oxide...and rubidium oxide . . . )" may cause undesirable noise (Loretz U.K. Patent Application GB 2 120 232 A, published Nov. 30, 1983). Loretz there taught this formulation free of potassium and rubidium:
______________________________________ Composition (mol Percent of Oxide) SiO.sub.2 68.00 PbO 24.00 Alkali Li.sub.2 O 1.60 Na.sub.2 O 2.80 K.sub.2 O -- Rb.sub.2 O -- Cs.sub.2 O 0.30 Alkaline Earth SrO 3.00 BaO -- As.sub.2 O.sub.3 0.06 Bi.sub.2 O.sub.3 0.04 Al.sub.2 O.sub.3 0.30 ______________________________________
It was asserted in Bateman U.S. Pat. No. 4,365,150, "Gain Stabilized Microchannel Plates and MCP Treatment Method", Dec. 21, 1982, that providing a cesium oxide film on channel walls improved gain and life. Bateman said also (col. 3, lines 33-37):
Results equivalent to that of the solution evaporation method can be achieved by incorporating the cesium in the raw glass used to fabricate the microchannel plate, suitably as a replacement for a portion of the potassium content.
Glass of the formula of the invention, except that it included in its ingredients several percent by weight of rubidium oxide, was in public use more than a year ago.